In e.Coli structural gene of lac operon is stimulated in:

*A. Presence of lactose and absence of glucose

B. Presence of lactose only

C. Presence of glucose and absence of lactose

D. Presence of galactose only

E. Presence of glucose only

CAP (Catabolite active gene protein) in Lac operon is an example of:

*A. Positive regulator of transcription

B. Negative regulator of transcription

C. Regulatory region of DNA

D. Constitutive expression

E. Attenuation

Amber codon refers to:

*A. Stop codon

B. Initiating codon

C. Mutant codon

D. Codon for more than one amino acid

E. Codon for Alanine

Amino acid with a single codon is:

A. Alanine

B. Threonine

C. Tyrosine

D. Phenylalanine

*E. Tryptophan

Point out the chemical nature of gene:

A. The fragment of Ribonucleic acid

B. Lipoprotein

C. Chromoprotein

*D. The fragment of Deoxyribonucleic acid

E. Glycoprotein

The degeneration of the genetic code is explained therefore:

A. Genetic Code is composed of various triplets

*B. Two or more triplets may be for one amino acid

C. “Punctuation marks” are absent in the genetic code

D. The Code is single for all biologic systems

E. Each amino acid is coded for one triplet, only

Which of the following acts on nuclear receptor:

A. Glucagon

B. Epinephrine

C. TSH

D. Growth hormone

*E. Estrogen

Which of the following hormone mechanism of action is associated with cyclic AMP formation in a target cell?

*A. Vasopressin

B. Aldosterone

C. Atrial natriuretic peptide

D. Angiotensinogen I

E. Renin

Metabolic product of epinephrine inactivation excreted in urine is:

A. Androstenedione

B. Estrone

*C. Metanephrine

D. Dopamine

E. Nor metanephrine

The following hormone does not have any intracellular receptor:

A. Calcitriol

*B. Adrenaline

C. Aldosterone

D. Cortisol

E. Thyroxine

Insulin mediated glucose uptake in myocyte is through:

A. GLUT 1

B. GLUT 3

C. GLUT 2

D. GLUT 5

*E. GLUT 4

Which of the following acts via cAMP

*A. LH

B. Thyroxine

C. All positions are correct

D. Estrogen

E. Testosterone

Find out the feature of releasing factors (RF) structure:

A. RF are amino acid derivatives

B. Both of RF contain sialic acid

C. RF are simple proteins with quaternary structure

D. RF are glycoproteins

*E. RF are short peptides

Nor-epinephrine is converted to epinephrine by:

*A. N-methylation

B. Dopamine hydroxylase

C. S-methylation

D. DOPA-decarboxylase

E. O-methylation

Name a membrane bound enzyme that catalyzes the formation of cyclic AMP from ATP:

A. ATP synthase

*B. Adenylate cyclase

C. RNA polymerase

D. Lactate dehydrogenase

E. Tyrosine kinase

Try to name a small Ca²⁺binding protein that modifies the activity of many enzymes and other proteins in response to changes of Ca²⁺ concentration.

A. Collagen

B. Elastin

*C. Calmodulin

D. Kinesin

E. Cycline

Point out the chemical nature of hormone receptors:

*A. Proteins

B. Vitamins

C. Lipids

D. Nucleic acids

E. Carbohydrates

Find out the type of activity that is considered for insulin-receptor complex function in the intracellular space of target cell:

A. cAMP-dependent proteinkinase activity

B. Similar to Phospholipase C activity

C. Tyrosine aminotransferase activity

D. cAMP-dependent polymerase activity

*E. Tyrosine kinase activity

Which of the following belongs to steroid superfamily

*A. Calcitriol

B. Epinephrine

C. Growth hormone

D. ACTH

E. Insulin

Thyroxine and catecholamine are derived from:

A. Leucine

B. Tryptophan

C. Alanine

*D. Tyrosine

E. Isoleucine

Which of the following acts through tyrosine kinase receptor?:

A. Glucagon

B. Follicle stimulating hormone

C. Growth gormone

*D. Insulin

E. Epinephrine

All are secondary messenger except:

*A. mRNA

B. cAMP

C. Diacylglycerol

D. Phosphatidyl inositol triphosphate

E. Calcium

Adenylate cyclase enzyme is inhibited by:

A. Calcitonin

B. Thyroxine

C. Epinephrine

*D. Somatostatin

E. Nor-epinephrine

Which of the following substances acts to increase the release of Ca²⁺from endoplasmic reticulum in muscular cell?

A. Diacylglycerol

B. 1,25-dihydroxy cholecalciferol

*C. Inositol triphosphate

D. Monoacylglycerol

E. Parathyroid hormone

For which hormone is cGMP secondary messenger?

A. Epinephrine

B. Cortisone

*C. Atrial natriuretic peptide

D. Growth hormone

E. Thyroxine

Adenylate Cyclase is activated of :

*A. GTP-dependant regulatory protein

B. Nuclear receptor

C. cAMP

D. Phosphodiesterase

E. Membrane receptor

The Simple goiter (enlarged thyroid) may be caused by:

A. Uncontrolled production of T3 and T4

*B. Iodide deficiency

C. Production of thyroid-stimulating IgG

D. Excessive intake of exogenous TSH

E. Decrease of TSH secretion